Method of making cold screw blanks, rivets, and similar headed articles



I 1618,446 Feb. 22,1927. JlKU-HNE,

METHOD OF MAKING com: SCREW sumxs, RIvE'rsfAND SIMILAR BEADED ARTICLES Orizinal Filed Jan.k2 8,- 1924 4 a h I 'FignZ d h s Fig.5

v Kwg N 1 q h r q B a: X g m I P \d Fr 7 a 1 k q FI'FB igr m b 3, x d lq; hL I 59 \w l '5 g n p q 111 r f b INVENTOR.

ATTORNEY Patented Feb. 22, r I

. 1,618,446 PATENT OFFICE...

. aosnrn ,KUHNE, or IsEnLouN, GERMANY.

Y METHOD or MAKING Conn sonnw BLANKS, RIVETS, AND SIMILAR BEADED An'rIoLEs.

7 Original application filed .lanuary 28, 192 1,. Serial No. 659,201, Patent No. 1,561,863, and in Germany June 26, 1922. Divided andthis application filed February 28, 1925. Serial No. 12,377.

This applicationl is divisionalof ma copending application No. 689,201, filed; anu- L al- 28, 1924., now. PatentlNoi 1,561,863,dated November 1.7, 1925. f Q v p The subject-matter of my invention is a method of manufacturing the coldrivets,"

screw-blanks and other bolt-like, headed articles by means of which a very great length of the stock or rod can be upset'to form the head so that the size of the head for acer- Y tain diameter of material is almost unlimited, the new method being thus especially adapted for producing voluminous heads, i. e.' heads the volume of'which equals to the Volume of a portion of the rod or stock whose-length is a multiple of the diameter of the rod. I

The essential feature of my invention con- I sists in this, that the end of the stock or rod is worked up into the form'of a head by the application of a single, -'oontinuou's pressure effected in this way. The rod end to be upset -is first of all surrounded by a sleeve orliollow plunger and .then, by the application, oftxpressure only on the crosssect-ion of the rod, is ressed out-of the sleeve andfinto the head: orming' mould or die space, wherein the mass of the rod-end becomes spread out or upset. Immediately on this but during the same pressuremovement the head is pressed into its final shapeby pressure exerted on the'entire face of the head. Both the preliminary and final pressures are effected during a singles'troke -of the press, the preliminary pressure by means of a punch guided in the plunger surrounding the rod-end, and the finalpressure being exerted commonly by the said v punch and by said plunger, which two after the head therefore has and uninterrupted course'and occuriduring quite a short period,

whereby the ro material flows in a satisfactory manner and detrimental structural changes and stresses are avoided. In con sequence, the products of the new method have ahigh deg'reeof strength, and -anneal ing of'the same isnnnecessary. The new method, moreover, has the advantage ofa high rate of production since at each pres sure movement or stroke a-finished article is produced. Furthermore, the: operating remain almost cold.

' only a respectively, produced according to the present inven-' appliances,i. e. the mould and stamping die These appliances are consequently subjected only to comparatively little wear. At the same time it is possible to increase the speed of'operation of the machine and therefore the output. Finally, comparatively simple .machine, namely, a so-called single pressure press, is necessary for carrying. out the new method.

Another feature of my invention consists of this that, after having spread out the rod end in the head-forming matrix, a small ,recess or depression is pressed into the front face of the bolt head, the bottom of said recess corresponding with the cross-section of the stock or rod. In this way the formation of a sharp edge or burr at the front face of the bolt head which otherwise may result from the mass of the stock flowing into the unavoidable intervening space between the preliminary pressure punch. and the hollow plunger surrounding said punch and the stock to be upset, is avoided.

My new method is more fully explained in the following description, reference being made to the annexed drawing which shows, by way of example, a constructional form of apparatus for carrying out said method. In the drawing Figs. 1 to 4 are four sectional side elevations of an apparatus which may be used in a machine performance of my method.

Fig. 1 indicates the position of the parts at the beginning of the pressure stroke.

Figs. 2 and 3 indicate two intermediate positlo'ns, and I Fig. 4 shows the position at the end of the pressure stroke.

a Fig. 5 is an axial, longitudinal section on a larger scale, of the matrix and the front end of the plunger surrounding the preliminary stamping punch in the end position of the pressure appliance, and

Figs. 6 and 7 are side and front views, of I a hexagon screw-head tion. I

- a is'a stationary die having a matrix a of the size and shape of the head to be formed. This matrix is so sunk into, the die a that the final stamping die must enter the matrix in order completely to close the matrix. 6 indicates the head of the reciprocating press-slide c, and f a sleeeve exchangeably mounted in the head. In this sleeve is guided a second sleeve 9' which is controlled by a spring h tending to press it outwardly, its outward movement being arrested by the screw d which engages in a groove of the sleeve 9. In the sleeve 9 is guided the hollow plunger 9 which together with the pressure pin it constitutes the tinal stamping die proper, and which is axially slidable in the sleeve 9 within certain limits. The plunger. (1 is controlled by a compression spring 1' which bears against its rear flange and against a shoulder on the sleeve g, said spring tending to force the plunger 11 into the sleeve A screw .9 engaging in a groove in the plunger (1 limits this movement in such manner that in the normal position the pressure face of the plunger (1 is flush with the front face of the sleeve The plunger 9 has a bore '5 of the diameter of the rod to be headed. In this bore is guided the pressure pin is which at its rear end bears against the larger thrust rod m, the large end it of the latter bearing against the adjustable key 0 of the slide 0. The

' thrust rod m has a shoulder m which, after a certain displacement of said thrust rod m and pressure pin is in the plunger 9, strikes against the rear end of the latter and then drives the plunger positively.

The total length 0% the pressure pin 70 and that portion of the thrust rod m which is in front of the shoulder m is so related to the length of the plunger g that at the end of that movement, of the preliminary stamping punch formed b pin is and rod m which is inde endent of tie plunger g, i. e. when the ro m, by means of its shoulder m positively engages the plunger 9, the front end of the pressure pin is will project a certain distance from the plunger g.

The operation of the described apparatus is as follows:

After the rod p to be headed has been fed through the die a the distance corresponding to the mass of material to be shaped, the press-slide c is moved leftwardly against the matrix a, the unch q and the sleeve 9 being slipped over tlie rod portion extending from the die a. As soon as sleeve 9 abuts against the die a the matrix or die chamber in the latter is closed or substantially closed laterally by this sleeve, while the plunger 9 will not yet have entered said die space, so that this space, bein enclosed'by die a, sleeve 9 and plunger 9, has a greater depth than the intended finished height of the head to be upset (Fig. 2). By striking against the matrix a the sleeve q and with it the plunger 9 are restrained rom further movement while the slide a and with it the rod m and pressure pin is advance with simultaneous compression of the spring it. During that time, the rod-portion projecting from the die a and penetrating the bore 2' in the plunger 9 is pressed by the pressure pin is into the die chamber or matrix al the mass being spread out laterally all round in said space (Fig. 3) As soon as the mass is pressed into the matrix the thrust rod m by means of its shoulder of, now located at the rear-end of the plunger 9, drives the latter forward while simultaneously compressing the spring r. In that way the plunger 1 and pressure pin Ir, which both now art in common as a final stamping die and enter the die a as such, completely spread and press out the mass in the matrix, that is, convert it to its final form. The slide 0 thereupon again moves rightwardly, the lunger and sleeve 9 returning to their initial positions by the action of springs 7' and h respectively (Fig. l). Simultaneous ly means not. shown in the drawing again advance the rod p and cut oil the finished article, whereupon the described operation is repeated. I

When pressing that portion of the rod 72 which is surrounded by the plunger 9 into the matrix a the pressure pin 7.; at its front end projects somewhat from the plunger 9 (Figs. 3, 4 and 5) and it keeps this position with respect to the plunger 9 also when the final pressing occurs. In that way, as Figs. 5-7 particularly .show, a small recess or de prcssion v is pressed into the front face of the bolt head, the bottom of which recess corresponding with the cross section of the pressure pin. The extension i. e., flattening out, of the face of the work-piece associated with that action completely eliminates the sharp edge or burr which would have formed at the end of the rod 79 adjacent to the pressure pin is when the mass of this rod-end is pressed into the matrix, such formation being due to the mass flowing into the unavoidable intervening space between the pressure pin in and the wall of the bore of the plunger The otherwise necessary extra work in removing the small annular burr from the front face of the bolthead is thus dispensed with.

The new method and the machine for carrying it into practice may be mo' dified. in this way, namely, the rod to be headed, instead of being fed through the die a, may be conducted through an opening laterally of the latter. In this case the blank is cut off in a manner known per se before being worked up by the pressure devices. The blanks cut off are then introduced between die a and plunger g by means of a carrier of a form known per se, the plunger-being advanced on to the blank, whereupon the pressing operations proceed in the manner already described.

The new step of pressin a deepening into the front face of the bolt head may be utilized, in the case of the heading of screws and the like, to form simultaneously on the front of the head either a slit for the lie insertion of a screw driver or a multiple sidedhole for the insertion of a key. In the first instance the pressure pin is has on its pressure face a projecting ribfor forming the slit in the screw-head, while in the second instance the pressure-pin I: and the bore of the plunger surrounding it have a polygonal cross sect on,.the pressure pin is projecting from the "plunger a;- distance equivalent to the desired" depth ofthe hole.

The advantages of my method-over prior methods are,',-briefly stated, as'follows: In making headed articles of the character set forth, two general processes are commonly employed. vIn one of these processes the stock is heated and upset while in. a heated state. strength, but the cost of manufacture is comparatively great because of the necessity of preliminarily heating the stock. In the other of these processes, commonly known as the cold process, the blank is upset in an .unheated state in two stages, i. e., by successive upsetting or swagi'ngactions. These actions are performed by a so-called double-pressure press. 1n whlch, on one stroke of the press, a plunger acts to force an enclosed end ofthe blank projecting beyond thematrix back into the matrix to form inchoate" head, and on asecond stroke of the machine a second lunger acts to press the inchoate head into ished head shape.

,Suchdouble-pressure presses, as heretofore constructed, are cumbersome and clumsy in construction, requlring the use of shifting means to successively dispose the plungers at different levels for working actions, they are slow in action because two working motions or cycles are required for the production of each article, and they are defective in operation because'of an inherent fault due to the fact that a measurable time interval occurs in the action upon the blank of the two working punch members. When the first punch member exerts its Working pressure on the blank a certain amount of heat is generated in the blank. I have' discovered that this amount of heat is sufficient to cause the "metal to flow readily under a succeedi g pressure if the metal is acted upon before the heat comes to the-surface, but that, unless the second pressure is immediately applied, the engendered heat passes to the'surface of the blank and is given off, allowing the blank to chill and cool. This chilling or cooling of the blank Articles so madepossess the requisite familiar havethis faultyi action, because of the: time interval ensuing between the operation of the punches, the stock chillingand cooling off after the first pressure is applied 1 toform the inchoate head and before theffi j v second pressure can be 7 pp to complete or finish the head.

. By the use of my method the expenseofj heating the blankprior to 'upsetting,"as in the heat swaging process, and the above-- I noted obj ections to the cold swaging process heretofore in use, are Wholly overcome. With my method, the instant the pressure stroke of the first pressure plunger k is completed, .the second pressuie plunger q comes into action, the two' plungers then moving togethe'r as a unit coaxially, whereby. immediately u on the formation of the inchoate head by t e plun er k the pressures of both plungers are app ied over thefull area of the inchoate head to flatten out. the same into finished head form. The successive actions are so'timed, and are so rapid,

that before the heat in the inchoate head 1 engendered by the stroke of plunger 70 can come to the surface, and-while the metalof the inchoate head is still therefore in a more or less fluent or plasticstate, the plunger q comes into action with theplunger k and the forces of both plungers are applied at a time when the material will readily and easily flow from one formation into the a type ofmachine'to be employed for carrying the method into practice in which the plungers operate without time intervals between the cessation of action of one and the beginning of the action of the other, so that heads of maximum strength will be produced without additional treatment of the article and a completearticle producedon each working stroke or cycle of action of the machine, the invention thus providing a method and lending itself to'the production of a machine whereby the production rate per working time of the machine is materially increased and the cost'of production accordingly reduced. Another advantage gained byfgmy method is that the rate,that each working action is completed before any active development of heat 1n the article, so that great working workin action may be performed at such I I a rapi speed of the machine can be obtained without the tools becoming scorched or injured to any degree by heat.

Claims:

1. The process of upsetting or heading a blank for the formation of a headed article, such as a bolt, rivet, or the like, which consists in providing a die having a head forming chamber of suitable sizeand shape and open at its front, disposing the blank in the die so that one end of theblank projects beyond the open front of the chamber, enclosing the projecting end of the blank with in suitable enclosing means, disposing the enclosing means so as to wholly or substantially close the front of the chamber at all sides about the blank, applying pressure to the enclosed projecting end of the blankin the axial line of the blank so as to force such projecting end of the blank from said enclosing means into the chamber in such manner as to laterally expand the same together with that portion of the blank normally contained in the chamber so as to form an inchoate head Within the chamber, then while said pressure is acting applying a second pressure within an area about the same for coaction therewith so that the sum of the areas of both pressures will be equal to the full area of the inchoate head, and simultaneously exerting both pressures upon the inchoate head to flatten it out and form a complete head. i

2. The process of upsetting or heading a blank for the formation of a headed article, such as a bolt, rivet, or the like, which consists in providing a die having a head fornr ing chamber of suitable size and shape and open at its front, disposing the blank in the die so that one end of the blank projects beyond the open front of the chamber, enclosing the projecting end of the blank Within suitable enclosing means, disposing the enclosing means so as to wholly or substantially close the front of the chamber at all sides about the blank, applying pressure to the enclosed projecting end of the blank in the akial line of the blank so as to force such projecting end of the blank from said enclosing means into the chamber in such manner as to laterally expand the same together with that portion of the blank normally contained in the chamber so as to form an inchoate head within the chamber, then while said pressure is acting applying a second pressure within an area about the same for coaction there with so that the sum of the areas of both pressures will be equal to the full area of the inchoatc head, simultaneously exerting both pre sures upon the inchoate head to flatten it out and form a complete head, and extending the range of the first-named pressure beyond that of the second-named pressure so as to formadepression in the crown of the head.

In testimony whereof I affix my signature.

JOSEPH KUHNE. 

